Molding apparatus

ABSTRACT

An elastomeric seal used in molding articles is disclosed. The seal has a first lateral cross-sectional dimension larger than the opening of a seal groove and at least a second lateral cross-sectional extending beyond the opening of a seal groove which is smaller than the lateral cross-sectional dimension at the opening of the seal groove. The elastomeric seal is releasably retained in the seal groove and provides an improved molding cavity for molding articles such as sanitary fixtures, i.e., tubs, whirlpools, spas, etc. Also disclosed, is a molding apparatus including the elastomeric seals useful in molding sanitary fixtures.

This is a division of application Ser. No. 07/931,436, filed on Aug. 19,1992, for ELASTOMERIC MOLD SEALS now U.S. Pat. No. 5,206,076, which is afile wrapper continuation patent application of application Ser. No.07/467,771, filed on Jan. 19, 1990 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to elastomeric seals used in moldingapparatus.

2. Background of Related Art

For years, porcelain-cast iron fixtures have been widely used. However,the drawbacks of the porcelain-cast iron and enamelled fixtures havealways been their susceptibility to impact damage .and their extremeweight which makes moving and installation of large fixtures such asbathtubs and whirlpools, most difficult. While the porcelain-cast ironfixtures have the advantage of providing a very solid feel and a highweight bearing capability, these drawbacks have made these tubs lessattractive to the purchasing public.

Initial attempts by the industry to replace these porcelain-cast ironfixtures, have been to introduce lighter and more resilient componentstructures, however, this has not been without difficulty. Some of theseattempts included thin stainless steel fixtures which were lighter thanporcelain-cast iron fixtures, but did not have the solid feel orstructural strength required for large articles such as bathtubs andwhirlpool tubs. Other attempts included composite structures which had aplastic, hollow feel, and would deform, crack, chip or delaminate whensubjected to impact, thermal shock or the weight of a typical bather.One successful solution to the above-mentioned shortcomings anddrawbacks of the prior art sanitary fixtures, is disclosed in U.S. Pat.No. 4,664,982 to Genovese, et al., the disclosure of which isincorporated by reference herein. U.S. Pat. No. 4,664,982 to Genovese,et al. discloses a composite enamel steel structure which has the lookand feel of the earlier porcelain-cast iron fixtures. The compositestructure is light, has high structural strength, and resistdelamination, chipping and denting due to impact or thermal shock. Thecomposite enamel steel fixture is formed from a steel shell, which istypically formed from a steel blank by a series of stamping and punchingoperations. The shell is then enamelled on both its finish andnon-finish sides. The enamelling process usually includes heating thesteel shell to high temperatures melting the enamel onto the shellsurface. This heating and subsequent cooling often results in slightbowing and distortion of the shell. The shell thusly formed is used as apart of a mold to form a layer of reinforced foam plastic by ReactionInjection Molding ("RIM") or by Reinforced Reaction Injection Molding("RRIM") processing on the non-finished (i.e., underside, of shell).

Commonly assigned U.S. Pat. No. 4,664,092 to Genovese, et al. and patentapplication Ser. No. 07/400,280 to Kuszaj, et al. both of which areincorporated by reference herein, describe polymeric foam backedenamelled-carbon steel or stainless steel plumbing fixtures that areresistant to chipping, cracking, crazing, delamination or deformationwhen subjected to impact from either the finish or non-finish side. Theuse of the aforementioned composite mold structures results in fixtureswhich have the feel of porcelain-cast iron and enamel fixtures, highimpact strength, and resistance to delamination. These compositestructures possess excellent physical and mechanical properties as aresult of the chemical bonding of the reinforced polymeric layer to theenamelled steel or stainless steel shell.

Another approach was to replace the enamelled-steel shell with apolymeric-cosmetic surface layer and binding that layer directly to afoamed plastic substrate to provide a high impact strength,delamination-resistant structure. This approach is disclosed in commonlyassigned U.S. Pat. Nos. 4,844,944 and 4,844,955 both to Graefe, et al.,the disclosures of which are incorporated by reference herein. Theseapproaches suffer from the same problems described above with regard tobowing, and warpage of the shell due to the irregularity in the shellfrom the manufacturing process. Co-pending U.S. patent application Ser.No. 07/458,598 to Marsilio et al. filed on Dec. 29, 1989 now U.S. Pat.No. 5,129,804, describes a molding apparatus which is suitable formolding a layer of reinforced polymeric material to the non-finish sideof a shell. The molding apparatus described in this application can beused with any of the shells and polymeric materials which are describedin U.S. Pat. Nos. 4,664,982, 4,844,944, 4,844,955 and 4,664,092 andapplication Ser. Nos. 07/400,280 and 07/458,598 as described above.

Typically, a shell having a finish and a non-finish side is insertedinto a female mold receptor forming a cavity between the moldingreceptacle surface and a non-finish portion of the shell. In order toclose the cavity and allow sufficient support to be applied during themolding operation, a male molding portion having a surface whichsubstantially conforms to the finished surface contour of the shell, isurged against the finished side of the shell. A cavity is formed betweenthe molding receptacle and the non-finish side of the shell. The cavitymust be sealed around the periphery of the shell to prevent leakage ofthe foamed polymeric material from the cavity. Accordingly, seals arerequired which can accommodate variations in the shape of the shellsresulting from the manufacturing process used. In one proposed sealingsystem which may be used, a molding apparatus includes a urethanecoating on an undersized male molding portion which matches the finishsurface of the shell. This protective urethane coating is molded on thesurface of the male molding portion in a space adjacent to the shellsfinished surface by injecting urethane in the space. The curedpolyurethane about the male molding portion forms a surface on the malemolding portion which contacts the periphery of the shell and a portionof a molding receptacle, so as to seal off a molding cavity between thenon-finish surface of the shell and a surface of the molding receptacle.

This molded sealing system suffers from several significant shortcomingsand drawbacks. In particular, the seal is cast as part of the protectiveurethane surface coating of the male mold portion. It is thereforedifficult and expensive to replace. Since such seals typically wear anddeteriorate over repeated molding cycles, such sealing systems are notdesirable. Also, due to variations in the shape of the shell due to themanufacturing process the shape of the molded seals may vary.Accordingly, it is extremely difficult and often impossible to form anadequately sealed molding cavity with each new shell into which thefoamed polymeric material can be introduced under adequate moldingpressure. Consequently, the foamed polymeric material flows beyond theseal and often damaging the finished surface of the shell, or adheringto the mold receptor.

In another proposed sealing system used in molding bathtubs, U.S. Pat.No. 2,841,823 discloses a molding apparatus for low pressure compressionmolding of laminates useful in fabricating large bulky objects such asboats or bathtubs. The mold includes an L-shaped baffle anchored in anupper molding block, extending outwardly and downwardly from the moldingblock and a lower molding block having a U-shaped channel which facesthe L-shaped baffle. An expandable hose is located in the U-shapedchannel. To form a seal, compressed air is introduced into the hose,causing it to expand and engage the L-shaped baffle.

This mold sealing system suffers from drawbacks however. In particular,the inflatable hose is only maintained in the U-shaped channel whenpressed against the L-shaped baffle. The inflatable hose requires asource of air under pressure to inflate the hose and engage the seal.Also, the inflatable hose may become dislodged from the U-shaped channelwhen the L-shaped baffle is lifted from the lower molding block.

U.S. Pat. No. 4,732,553 discloses a seal assembly for molding gasketsaround the periphery of a window. It also includes fluid filled bladderswhich are located in both the upper and lower portions of the moldingapparatus. Silicone seals rest above the bladders within seal grooves.The inflatable air bladders within the mold seal groove adjust thenon-compressible seal to engage the molding cavity. These seals,however, are maintained in the groove by adhesives and therefore are noteasily released from the seal groove.

U.S. Pat. Nos. 4,688,752 and 4,854,599 also disclose sealing systemswith seals in both the upper and lower cooperating mold sections. Thesepatents describe seals which are retained within a mold seal groove by aclamp. In addition, these patents disclose the use of non-elastomericfluorocarbon materials such as Teflon making up part of the seal. Thesenon-elastomeric components therefore are unable to accommodate for theinherent distortion present in sanitary fixture shells as discussedabove.

In response to the above problems associated with the prior art sealingsystems proposed above, an alternative sealing system has been proposedby Applicants. In this proposed sealing system, a seal groove is formedin the male mold portion above the upper flange of the shell andadjacent the cavity form between the non-finished surface of the shelland the female mold, when the molding apparatus is in its closedposition. In the seal groove, segments of urethane material are insertedend-to-end to form a seal which is retained in the male mold portion byan overhanging edge projection formed by the protective urethane surfacecoating on the male mold portion. While such a proposed sealing systemprovides a seal which can be replaced, it is not done withoutdifficulty. In addition, it suffers from additional shortcomings anddrawbacks as well. In particular, the overhanging edge projection of theprotective urethane surface coating on the male mold portion, fails toadequately retain the seal in the groove of the male mold portion duringdemolding operations, and as with other proposed sealing systemsdescribed above, it is incapable of establishing an effective seal alongall engaging surfaces of the shell and seal due to the inherentvariations of the shell due to bowing, warping and distortion of theshell due to manufacturing processes.

In view, therefore, of the shortcomings and drawbacks of the proposedprior art methods, and apparatus for effecting a seal between the shelland molding surface of a mold receptor used to mold products therein,there is a clear need to provide a sealing system that overcomes theabove described shortcomings and drawbacks.

Accordingly, it is a primary object of the present invention to providea seal for a molding receptacle for applying a coating to the undersidesurface of a sanitary fixture shell, wherein the seal is capable ofbeing releasably retained within a groove contained in either the moldreceptor or male molding means.

It is another object of the present invention to provide a seal havingat least a first and second layer of elastomeric material which isreleasably retained within a seal groove and is capable of accommodatingfor the shell variations which are inherent to the shell due to themanufacturing process.

It is a further object of the present invention to provide a moldingapparatus having an improved seal and retaining means.

It is a further object of the present invention to provide a moldingapparatus with a sealing system capable of accommodating variations insanitary fixture shells due to the manufacturing process of the shells.

SUMMARY OF THE INVENTION

These and other objects are achieved by the present invention whichprovides an elastomeric mold seal and molding appartus having theinventive elastomeric mold seal, both of which are useful in moldingsanitary fixtures such as bathtubs and whirlpool tubs. The seal of thepresent invention is releasably retained in a mold seal groove. The sealhas a first lateral cross section completely contained within the sealgroove. The first lateral cross-sectional dimension is larger than thelateral cross section of the opening of the seal groove, thus providingenhanced retention properties for the seal. The seal of the presentinvention also has a second lateral cross-sectional dimension which issmaller than the lateral cross-sectional dimension of the opening of themold seal groove and extends beyond the mold seal groove opening toengage a molding surface.

The seal of the present invention is preferably composed of anelastomeric material such as polyurethane having between 20 to about 80Shore A durometer value. Alternatively, the seal of the presentinvention may be composed of at least two materials of varying durometervalues. In a preferred embodiment, the durometer value of the firstlayer of elastomeric material which completely resides within the moldseal groove is less than that of the second layer which extends beyondthe opening of the mold seal groove. The elastomeric properties of theseal allow the seal to expand and seal the opening of the seal groovewhen the seal is engaged under pressure to a second molding surface.

The improved retention qualities of the inventive mold seal is achievedin one embodiment by seals having a trapezoidal lateral cross section.Alternatively, the retaining feature of the seals is achieved by saidseal having a seal flange for engaging a recess positioned on theinterior of the seal groove beyond the opening of the seal groove. Theflange may be further described as having a first rectangular lateralcross .section which is joined to a second rectangular cross sectionwhich extends beyond the opening of the seal groove.

Also disclosed is a molding apparatus capable of being selectivelyopened and closed for molding and demolding operations having a moldingreceptacle capable of receiving a sanitary fixture shell and defining avoid between the shell and the molding surface of the moldingreceptacle. A molding apparatus further includes a male molding memberwhich has a surface which substantially conforms to the surface contourof the shell to apply sufficient pressure to the shell during moldingprocess. The molding apparatus is also configured to contain a mold sealwhich may reside in either the male molding member or on the top surfaceof the molding receptacle. The seal assists in forming a closed cavityaround the periphery of the shell and the molding surface of the moldingreceptacle. The seals are composed of elastomeric materials whichprovide superior accomodation of the variations in the shape of theshells which result from the manufacturing of the shells.

In a preferred embodiment, the seals have at least two layers ofelastomeric material having differing durometer values. Also included isa seal having a trapezoidal shape such that the first lateralcross-sectional dimension is larger than the opening of the mold sealgroove to assist in retaining the seal within the groove and at least asecond lateral cross-sectional dimension which is smaller than thelateral cross-sectional dimension of the seal groove so as to allow thesecond lateral cross-sectional dimension to extend beyond the opening ofa seal groove so that the seal may engage in molding surface.

For a better understanding of the present invention, reference is madeto the following description, taken in conjunction with the followingfigures, the scope of which is pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a sanitary fixture shell to which areinforced foam plastic coating is applied during a RIM or a RRIMprocess;

FIG. 2 is a side view of the sanitary fixture shell taken along line2--2 of FIG. 1, illustrating inherent variations (i.e. presence of adistortion contour) in the horizontal direction along the upper flangeof the shell, caused during manufacturing operations;

FIG. 3 is a side view of the sanitary fixture shell taken along line 3of FIG. 1, illustrating inherent variations in horizontal directionalong the upper edge of the shell due to manufacturing operations;

FIG. 4A is a perspective schematic diagram of a molding receptacle usedin RIM and/or RRIM processes showing a mold having a molding surface anda male molding member having a protective surface coating, with asanitary fixture shell interposed therebetween;

FIG. 4B is an elevated side view of a molding apparatus illustrated inFIG. 4A, shown with a mold press used for closing the male moldingmember down onto the molding receptacle with the sanitary fixtureinterposed therebetween under molding pressures;

FIG. 5 is a side view of a molding receptacle shown in FIG. 4A withoutthe sealing system of the present invention, showing the existence of adistortion contour along the length of the seal, between the upperflange ends of the sanitary fixture shell and the seal, due tovariations in shell contour which result during manufacturingoperations;

FIG. 6A is a perspective view of a molding receptacle showing theelastomeric seal of the present invention in the seal groove, with aportion of the seal broken away for purpose of illustration;

FIG. 6B is a perspective view of a molding receptacle and a male moldingmember, with a sanitary fixture shell interposed therebetween, with theelastomeric seal system of the present invention in place and with themolding apparatus approaching its closed position, and where a portionof the male molding member, the elastomeric seal of the presentinvention, and shell are shown broken away;

FIG. 6C is a perspective view of a molding receptacle and a male moldingmember, with sanitary fixture shell embraced therebetween, with theelastomeric seal system of the present invention in place and with themolding apparatus in its closed position, and where a portion of themale molding member, sealing system of the present invention, and shellare shown broken away;

FIG. 7 is an elevated cross-sectional view of the molding apparatus andsealing system of the present invention shown in FIG. 6C, taken alongline 7--7, illustrating the elastomeric seal within a seal groove andits capability of adapting to variations in the shell due tomanufacturing processes to provide a perfect seal during moldingoperations;

FIG. 8A is a cross-sectional view showing a sanitary fixture shellembraced within the molding apparatus in its open position, and where anelastomeric seal of the present invention is installed within a sealgroove on the molding receptacle.

FIG. 8B is a cross-sectional view showing a sanitary fixture shellembraced within the molding apparatus in its closed position, with anelastomeric seal of the present invention installed within a seal grooveon the molding receptacle.

FIG. 9A is a cross-sectional view showing a sanitary fixture shellembraced within the molding apparatus in its open position, and where anelastomeric seal of the present invention is installed within a sealgroove on the male molding member;

FIG. 9B is a cross-sectional view showing a sanitary fixture shellembraced within the molding apparatus in its closed position, with anelastomeric seal of the present invention installed within a seal grooveon the male molding member;

FIG. 10 is a cross-sectional view of an elastomeric seal made inaccordance with the present invention installed within a seal groove onthe male molding member.

FIG. 11 is a cross-sectional view of an elastomeric seal made inaccordance with the present invention showing the seal having a firstand second elastomeric layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 4A through 11 in particular, the preferred embodimentofa molding system constructed in accordance with the principles of thepresent invention will now be described in detail as follows.

In general, the method and apparatus of the present invention isapplicablebetween a wide variety of apparatus used in applying areinforced plastic coatings to the underside surface of a shell, such asthose used in forming sanitary fixtures, including bathtubs, sinks,whirlpool bathtubs, spas, therapeutic tubs and the like, however, forpurposes of illustrationonly, the general concepts and principles of thepresent invention are herein illustrated in apparatus for applying areinforced polymeric coating to a bathtub. As used hereinafter, and inthe claims, the term "sanitary fixtures" shall be understood to includeall of the above-mentioned sanitary fixtures, and other types of liquidcontaining vessels, in which water is contained.

In FIG. 4A, there is shown molding apparatus used in applying areinforced polymeric coating against the side surface of a shell 1, asdescribed, forexample, in copending U.S. patent application Ser. No.07/458,598 filed on Dec. 29, 1989, now U.S. Pat. No. 5,129,004 andincorporated by reference herein. In general, the molding apparatuscomprises a molding receptacle unit 6 placed on a stationary platform 13and a male molding member 7. Themolding receptacle includes a moldingsurface 8 generally corresponding to the surface geometry of theunderside surfaces of the shell 1 to which thepolymeric coating is to beapplied. About the substantially planar deck portion 10 of the moldingreceptacle, there is formed a seal groove 9 in the planar deck portion10 of the molding receptacle unit 6.

As illustrated in FIG. 4A, the seal groove 9 extends about the perimeterofthe molding receptacle surface 8 and extending continuously so as toenclose form a groove in the shape of a substantially rectangular loop.

While not shown in FIG. 4A, the molding receptacle is provided with atleast one aperture formed in the molding surface which communicates withamix head 38 as shown FIG. 4B for introducing a hardenable polymericfoam material into the molding cavity (i.e. void) created between themolding surface 8 and the non-finish surface 4 of the shell. Also, aplurality of ejectors positioned in the molding receptacle unit 6, andserve to separate and eject a molded bathtub from the molding receptacleafter the RIM or RRIM molding process has been completed. Preferably,the ejectors are cylindrical rods which are hydraulically activated froma recessed position to an ejector position and visa versa.

The male molding member 7 in general comprises a support surface 11having a surface geometry of the bathtub shell 1. This support surfacebears a protective coating 12 formed from materials such as urethaneattached to the pressure applying surface 11 to provide a soft resilientsurface whichprovides support to the shell during molding operations,without damaging the finish surface 5 thereof.

Referring to FIG. 4B, there is shown a molding receptacle 6, and a malemolding member 7 attached to a stationary platform 13 and a translatableplatform 14, respectively of a mold press 15. The mold press alsoincludesa hydraulically operated system 16 which lowers and retains themale molding member 7 against the bathtub shell 1 on the finish surface5 thereof and the non-finish surface 4 of the shell adjacent with themolding surface 8 of the molding receptacle 6 during the moldingprocess. In such a lowered position, a molding cavity 18 is formedbetween the non-finish surface 4 of the shell and the molding surface 8of the moldingreceptacle 6, as particularly illustrated, for example inFIG. 6C. A mold press 15 which is suitable for molding bathtubs inaccordance with the method and apparatus of the present invention ismanufactured by Linden Industries, Inc.

Referring now to FIG. 6A, the molding receptacle unit 6 is shown with anelastomeric seal 40 installed within a seal groove 9 which is continuousabout the deck portion 10 of the mold receptacle. A portion of the seal40shown broken away to illustrate the structure of the seal.

The elastomeric seal is preferably constructed from urethane-basedmaterials in a manner well known to those skilled in the art. Theurethane, for example, may be obtained from Uniroyal as VIBRATHANE ®6020 or VIBRATHANE ® 8011. In addition thereto, the urethane is combinedwith a plasticizer such as BENSOFLEX ® 9-88 S.G. available from VelsicolChemical and curatives such as 1,4-butanediol available fromKodak orISONOL93 ® from Dow Chemical. The urethane based seals are prepared uponspecific need so that the amounts of the above ingredients may bevaried, as well known to those skilled in the art, to adjust thedurometer value of the resultant seal.

The elastomeric seal is further defined as having a Shore A durometerhardness value of from about 20 to about 80, preferably from about 35 toabout 45, and most preferably 39 to 41.

In a preferred embodiment, the seal is composed of at least two layersof differing durometer elastomeric materials, which is illustrated inFIGS. 8A, 8B, 9A, 9B and 11. The first layer of elastomeric material hasa cross-sectional dimension which is completely retained within the sealgroove 9. The lateral cross-sectional dimension of this first layercooperates with the seal groove 9 as defined by the opposing side walls21, bottom wall 20 and opening 22. The cross-sectional dimension of thefirst layer of elastomeric material is further defined as being largerthan the lateral cross-sectional dimension of the opening 22 of the sealgroove 9, thus providing a seal retention feature for retaining the sealwithin the groove. This structure greatly reduces the heretoforefrequently unavoidable and time consuming process of re-inserting thesealduring operational runs due to the tendency of the seals to becomedislodged from the seal groove upon demolding.

The first layer of elastomeric material preferably has a durometer valueoffrom about 35 to about 45 and more preferably from about 39 to about41. Ithas been found that elastomeric materials having theabove-mentioned durometer values provide superior ability to be retainedwithin the seal groove during demolding operations, while at the sametime providing the molding apparatus operator with sufficientflexibility to retrieve the seal from the seal groove when necessary.

In this preferred embodiment, there is provided at least a second layerof elastomeric material joined to the first layer. The second layer ofelastomeric material has a lateral cross-sectional dimension which issmaller than the lateral cross-sectional dimension of the opening 22 ofthe seal groove 9 and extends slightly beyond the opening of the moldsealgroove to engage a molding surface, for example the non-finish sideof a sanitary fixture shell. Preferably, the second layer of elastomericmaterial differs in hardness value than the first layer.

The durometer value of the second layer of elastomeric material in thisembodiment is from about 35 to about 80 Shore A durometer and morepreferably from about 60 to about 80. Alternatively, the seal may becomposed of at least two layers of elastomeric material wherein thedurometer value of the second layer of elastomeric material is abouttwicethat of the first layer.

Since the seal is composed of elastomeric materials, when engaged in themolding apparatus, the seal expands within the opening of the sealgroove to form a better seal during molding operations. The shape of theseal assists in retaining the seal in the seal groove during demoldingoperations when the male molding member 7 is pulled away from themolding receptacle 6. This seal retention feature of the presentinvention is mostimportant since the upper flange edge 2 of the shelland the cured, foamed reinforced polymeric material 25 typically adhereto the top surface 43 ofthe seal 40 during demolding operations, causingforces on the seal which attempt to pull the seal out and away from theseal groove 9. If the seal 40 is removed from the seal groove 9 duringdemolding operation, this disengagement of the seal requires the manualreinsertion of the seal in the groove. This reinsertion step thereforecan be time consuming, laborious, and costly from the manufacturer'spoint of view. Thus, the seal retention feature of the presentinvention, which is realized by having a first layer of elastomericmaterial having a first cross-sectional dimension which is larger thanthe opening of the seal groove and a second layer of elastomericmaterial joined to said first layer having extending beyond the openingof the seal groove allows for a molding apparatus to have approvedmolding operations.

Referring now to FIG. 5, there is shown a typical bathtub shell 1 whichis positioned under a male molding member 7 which is not closed downupon themolding receptacle 6. The elastomeric seal 40 is retained withinthe seal groove 9. As shown, the height of the seal extends beyond theseal groove opening 22 and is substantially parallel with the deckportion 10 of the molding receptacle 6. In a seal used in moldingsanitary fixtures, for example, the seal groove is about 500 thousandthsof an inch deep and the seal is such that it extends about 60thousandths of an inch beyond the seal groove opening 22, having aheight dimension of 560 thousandths of aninch. The elastomeric seal mayalso rest upon a shim 50 which is placed in the seal groove, but where ashim is used, the seal groove is deepened so that the seal, which, inthis illustrative embodiment maintains only a slight, about 60thousandths of an inch, extension beyond the seal groove opening 22.

When the multi-layered elastomeric seal embodiment is used, the firstlayerof elastomeric material comprises about 65% of the seal's heightdimension and the second layer comprises the remaining 35%.

FIGS. 2 and 3 show a distortion contour 100 formed between the upperflangeedge 2 and the top surface of the seal 43 when the moldingapparatus is in the opened position. Typically, the gaps which occur dueto the manufacturing process of the sanitary fixture shell range fromabout 0 (orflat) to about 0.094 inches. The elastomeric seals of thepresent inventionaccommodate for the inherent variations of the shellfrom flat up to about 3/32 of an inch. In addition, furtheraccommodation of the inherent variations of the shell greater than the3/32 of an inch amount can be achieved by adding a shim apparatus asdisclosed in co-pending applicationentitled, "ADJUSTABLE SHIMS FOR MOLDSEALS" filed by the present inventors concurrently herewith.

FIG. 7 shows the molding apparatus as depicted in FIG. 5 in the closedposition. The elastomeric seal of the present invention is seenaccommodating for the inherent distortion of the sanitary fixture shell.

Referring now to FIGS. 8A and 8B, a more detailed view of one embodimentofan elastomeric seal prepared in accordance with the present inventionas shown. In this embodiment, the seal groove 9 comprises a bottom wall20 opposing side walls 21 and an opening 22 for accepting the seal 40.The molding cavity 18 is completely sealed between the non-finishsurface 4 ofthe shell 1 and the molding surface 8.

Referring now to FIGS. 8A and 8B in particular, there is shown a seal 40made in accordance with one embodiment of the present invention placedwithin a seal groove and contacting a shim 50 placed on the bottom wall20of the seal groove. The seal has a first layer of elastomeric material42 completely retained within said seal groove and accounts for about65% of the seal's height dimension. The first layer of elastomericmaterial has side walls 41 contacting a portion of the side walls 21 ofthe mold seal groove. The lower portion 43 of the side wall of the firstlayer extends beyond the cross-sectional dimension of the opening 22 ofthe mold seal groove 9 to facilitate retention of the seal 40 within theseal groove.

The second layer of elastomeric material 44 is shown joined to the firstlayer of elastomeric material 42. This second layer extends beyond theopening 22 of the mold seal groove 9 and comprises the remaining 35% ofthe seal's height dimension. This second layer has side walls 45parallel to and in contact with the side walls 21 of the mold sealgroove. A top surface 49 is also provided on the second layer ofelastomeric material toengage the upper flange edge 2 of the shell 1when the shell is placed within the molding receptacle 6.

Referring now to FIGS. 9A-11, there is shown another embodiment of thesealof the present invention. As was described above, the seal asconfigured inFIGS. 9A and 9B in the molding apparatus 70 willaccommodate a slight distortion contour inherent along any particularupper flange edge 2, evenwithout a shim when the male molding member 7is configured with a seal groove 9 having a trapezoidal seal 80contained therein. The trapezoidal seal has a top surface 82 extendingbeyond the opening of 22 of the mold seal groove 9 by virtue of having across-sectional dimension smaller thanthat of said opening of said sealgroove. The seal also includes a bottom surface 84 resting against thebottom wall 20 seal groove 9. This bottom surface has a cross-sectionaldimension larger than the cross-sectional dimension of the opening 22 ofthe mold seal groove 9. Side walls 86 join the top and bottom surfacesin a manner which completes the trapezoidal shape. Side walls contactthe side walls 21 of the mold seal groove.

The angled shape of the seal in this embodiment, as facilitated byangular side walls 86, exhibits vastly superior sealing qualities due toexpansionof the seal in the seal groove. It also results in superiorretention qualities for maintaining the seal in the seal groove,especially during the demolding phase of the molding operation.

In this embodiment, the seal may be either of a single elastomericlayer, such as polyurethane or may be composed of at least two layers ofpolyurethane having varying hardnesses. For example, in moldingelastomeric materials, such as sanitary fixtures, such as bathtubs, theseal has a height dimension of 560 thousandths of an inch with about 60thousandths of an inch typically extending beyond the opening 22 of theseal groove 9. As stated above, the seal 40 is configured to contain afirst cross-sectional dimension 81 which cooperates with a bottomsurface of a seal groove 20 which is larger than a lateralcross-sectional dimension of an opening of the seal groove 9.

The elastomeric materials which make up the seal of this embodiment areselected from commercially available polyurethane type materials such asREN® by Ciba-Geigy item No. 6400 having a durometer reading of 50 asmeasured on the Shore A method. The range of acceptable durometervalues, however, range from about 20 to about 80. However, a preferredrange is between about 35 to about 45 durometer as measured by the ShoreA scale with a most preferred being 40 durometer. It is also to beunderstood thatthe durometer readings of the elastomeric seals made inaccordance with thepresent invention may vary plus or minus 3.

Referring now to FIG. 11, there is shown a seal in accordance with thepresent invention having a trapezoidal shape made of at least two layersof elastomeric material. In this alternative embodiment, the durometervalue of the first layer elastomeric material 42 is from about 35 to 40with a preferred durometer value of 40. The first layer comprises about65% of the total seal height dimension and resides completely within theseal groove 9. At least a second layer of elastomeric material is joinedto the first layer. The second layer comprises the remaining 35% of theseal and preferably has a durometer value of between 45 and 80 with apreferred value of about 55, Shore A. When the above described seals areused in molding apparatus for molding sanitary fixtures such asbathtubs, the seal groove 9 is about 500 thousandths of an inch deep andthe elastomeric seal 40 retained therein is about 560 thousandths of aninch, allowing 60 thousandths to extend beyond the mold seal grooveopening 22. When the molding apparatus 70 is employed using theelastomeric seals of the present invention, the molding cavity 18 formedwhen the shell 1 placed between cooperating mold receptacle 6 and mademolding member 7 is complete between the non-finish surface 4 of theshell and the molding surface 8 of the molding receptacle. In addition,it has been found that the seals of the present invention and moldingapparatus configured to contain such seals demonstrate superior abilityto accommodate inherent variations in shells used in the molding ofsanitary fixtures while at thesame time demonstrating improved abilityto be retained within seal grooveswhich can be located in either themale molding member, molding receptacle or seal.

Thus, while there have been described what are presently contemplatedpreferred embodiments of the present invention, further changes andmodifications could be made by those skilled in the art withoutdeparting from the scope of invention, and it is contemplated to claimall such changes and modifications.

What is claimed is:
 1. A molding apparatus capable of being selectivelyopened and closed for molding and demolding operations comprising:(a) amolding receptacle for receiving a shell having a finish and anon-finish side, said molding receptacle having a molding surface fordefining a void between said non-finish side of said shell and saidmolding surface; (b) male mold closing means for applying sufficientpressure to said shell during the molding operation; (c) a seal grooveand a self-retainable elastomeric seal, said seal groove in one or moreof said molding receptacle, said male mold closing means or said shelladapted for releasably retaining said elastomeric seal, said seal groovecomprising an open end and a closed end, the lateral cross-sectionaldimension at said open end being smaller than the lateralcross-sectional dimension at said closed end, said elastomeric sealadapted for closing said void between said non-finish side of said shelland said molding surface when said mold is closed, said elastomeric sealcomprising a first lateral cross-sectional dimension for cooperationwith an inside surface of said seal groove in a first molding surfacewhich is larger than said lateral cross-sectional dimension of said openend of said seal groove, and a second lateral cross-sectional dimensionextending beyond said seal groove which is smaller than said lateralcross-sectional dimension at said open end of said seal groove, wherebysaid elastomeric seal is retained within said seal groove when saidmolding apparatus is opened, and wherein said first lateralcross-sectional dimension comprises a first layer of elastomericmaterial having a first hardness value and said second lateralcross-sectional dimension comprises a second layer of elastomericmaterial joined to said first layer for engagement to a second moldingsurface, said second layer having a different hardness value than saidfirst layer.
 2. The molding apparatus of claim 1, wherein said shell isshaped for molding a sanitary fixture.
 3. The molding apparatus of claim2, wherein said sanitary fixture is selected from the group consistingof bathtubs, spas, shower receptors, whirlpools, sinks and toilets. 4.The molding apparatus of claim 1, wherein said seal groove is adaptedfor positioning said seal around the periphery of said shell.
 5. Themolding apparatus of claim 1, wherein said seal comprises a plurality ofelastomeric seal segments.
 6. The molding apparatus of claim 1, whereinsaid second layer has a hardness value greater than said first layer. 7.The molding apparatus according to claim 1, wherein the hardness valueof said first layer is in the range of from about 35 to about 45 andwherein the hardness value of second layer of material is from about 60to about 80 Shore A durometer.
 8. The molding apparatus of claim 1,wherein the hardness value of said first layer is from about 30 to 41and wherein the hardness value of said second layer is from about 52 toabout 55 Shore A durometer.
 9. The molding apparatus of claim 1, whereinsaid second layer has a hardness value at least twice as hard as saidfirst layer.
 10. The molding apparatus of claim 1, wherein said seal hasa hardness value of from about 20 to about 80 Shore A durometer.
 11. Themolding apparatus of claim 1, wherein said seal has a hardness value offrom about 35 to about 45 Shore A durometer.
 12. The molding apparatusof claim 1, wherein said seal has a hardness value of from about 39 toabout 41 Shore A durometer.
 13. The molding apparatus according to claim1, wherein said seal has a trapezoidal lateral cross section.
 14. Themolding apparatus according to claim 1, wherein said seal expands toseal said open end of said seal groove when said seal is engaged underpressure to said second molding surface.
 15. The molding apparatusaccording to claim 1, wherein said first lateral cross-sectionaldimension includes a seal flange for releasably retaining said seal insaid seal groove.
 16. The molding apparatus according to claim 15,wherein said flange is a two-sided flange for engaging a recess withinsaid seal groove, said recess is positioned on the interior of said sealgroove beyond said open end.
 17. The molding apparatus according toclaim 15, wherein said flange includes a first rectangular lateral crosssection which is joined to said second layer of elastomeric materialhaving a second rectangular cross section.
 18. The molding apparatus ofclaim 1, wherein said seal groove is in said mold receptor.
 19. Themolding apparatus of claim 1, wherein said seal groove is in saidclosing means.
 20. The molding apparatus of claim 1, wherein said moldclosing means comprises a male mold member.